Solution to resist poisoning in the integration of 248- and 193-nm photoresists with low-k dielectric materials

Integration of Low‐ k Dielectric Films in Damascene Processes

“…After lithography, incomplete resist development ( Figure 5.10a) leads after etch to unwanted fences in trenches around vias ( Figure 5.10b), and eventually, after metal fi lling, to bad electrical contact (open) between via and top metal line. This resist poisoning effect is amplifi ed by an interaction of several factors: resist, materials, integration architecture and integration processes [63,92]: their respective implications in the via poisoning phenomenon are described: resists are then very sensitive to any alkaline contamination, since the latter can neutralize these reactions. Very small concentrations (a few ppb) of airborne amine are known to easily contaminate DUV resists [93].…”

“…This leads to incomplete resist development and localized residues, inducing unwanted masking during the following etch step. In addition, all materials or processes containing nitrogen (as SiC x N y barrier layers and etching or stripping chemistries) can also generate amines (mostly by reaction with moisture) and then induce resist poisoning [63,92].…”

“…Suppression of all amine sources (material and processes without nitrogen [63,92]), or resist robustness improvement [91] minimize the problem ( Figure 5.11b), but cannot really eliminate it. Nevertheless, an architecture modifi cation, e.g., using a dual hard mask (see Figure 5.6) to prevent any contact between the resist and the low-k material, can offer a defi nite solution [89,100].…”